Abstract:Printed circuit usually makes up of microstrip lines ,circuit elements and other parts of fine structures.using traditional FDTD method to simulate the electromagnetic interference of PCB board irradiated by Electromagnetic wave will lead to low computation efficiency due to a large amount of grids .In this paper,a novel hybrid algorithm in FDTD is proposed，in which the Nonuniform FDTD method and multi grid lumped element FDTD method are integrated together.As an example, the coupling problem of microstrip circuit with lumped elements excited by electromagnetic pulse is simulated and it is observed that the Transient voltage and current response of lumped elements can be rapidly obtained.Then the correctness of the hybrid method is verified with comparing with the simulation results of electromagnetic software based on the finite integral method.Finally the influences of types of electromagnetic pulses and the space between microstrip lines on the electromagnetic coupling of the printed circuit are analyzed.